Pipelining

OCR Consultants is designing a computer for a large company.

OCR Consultants is designing the architecture of the CPU.

Compare two differences between the Von Neumann architecture and the Harvard architecture.

OCR Consultants is considering using pipelining.

State two benefits of using pipelining.

OCR Consultants can base the CPU around a RISC architecture or a CISC architecture.

Compare two differences between a RISC architecture and a CISC architecture.

Describe a benefit of making the CPU a multicore CPU.

* The employees of the large company work remotely from home and use large databases that store a lot of sensitive data. They need to be able to use the databases to search and sort data quickly.

OCR Consultants is considering two approaches:

• thin client approach – this is where the database is stored virtually on a remote server. All of the data processing is also completed on a remote server on virtual machines. The employees’ computers are only used to capture the data input and display the results from the virtual machines

• thick client approach – this is where most of the processing is done on the employees’ computer using specialised software to access the remote database.

Discuss the benefits and drawbacks of each of these approaches.

You should include the following in your answer:

• what is meant by virtual machines and virtual storage

• the benefits and drawbacks of a thin client and thick client approach described in the question

• a conclusion justifying which approach would be most suitable for this scenario.

The stored program concept uses the Fetch-Decode-Execute cycle to get the next instruction from memory and then execute it.

Describe what happens during the fetch stage of the Fetch-Decode-Execute cycle.

You should state the different registers and buses that are used in your answer.

One of the instructions that may be fetched and executed as part of this cycle is a branch instruction.

State the name of the register that would be altered in the execute phase during a branch instruction.

Three ways of improving the performance of a CPU are increasing the clock speed, adding more cores and using pipelining.

Explain how pipelining improves the performance of a CPU.

The Fibonacci sequence is a series of numbers. It starts with the number 0 and then 1. Each number after that is a sum of the two numbers before it.

The first seven numbers in the series are: 0 1 1 (i.e. 1 + 0) 2 (i.e. 1 + 1) 3 (i.e. 1 + 2) 5 (i.e. 2 + 3) 8 (i.e. 3 + 5)

Orla has written some code to show the first five numbers in the Fibonacci sequence (0,1,1,2,3) using the Little Man Computer (LMC) instruction set.

The LMC code that Orla has written contains an error.

State the five outputs that Orla’s code would give.

In Orla’s LMC code, she used direct memory addressing.

Give three other modes of memory addressing.

Since the development of high level languages, the use of assembly languages has reduced.

Give two reasons why in some circumstances programmers will choose to write code in assembly language.

The performance of a computer system can be improved by adding more RAM.

Explain why adding more RAM will improve the performance of a computer system.

A charity uses a desktop computer to record financial donations that it receives. The computer contains a single core, 2.4GHz processor with 2MB cache.

The processor uses the Von Neumann architecture.

Describe what is meant by the term ‘Von Neumann architecture’.

Give one way that the Harvard architecture differs from the Von Neumann architecture.

The charity is concerned that the performance of the computer is not sufficient and wishes to replace the processor.

Give two features of a replacement processor that would increase the typical performance of the computer.

Fig. 1 shows assembly code written using the Little Man Computer (LMC). The program calculates and outputs the total amount that is donated to the charity in any particular day. Depending on the amount, an additional bonus may be added to each amount donated.

The program shown in Fig. 1 is run once using three different inputs. Therefore, while the program is running once, it will output the updated total three times.

Give the total values that are output when the values 10, 50 and 120 are input into this program.

Write LMC code that will reset the value of the memory location labelled total to zero and then stop the program.

This program is run on a processor that allows pipelining.

Define the term ‘pipelining’.

Explain one benefit to the charity of using a processor that allows pipelining.

The processor contains registers including the accumulator and the program counter. The contents of these registers are modified during the Fetch-Decode-Execute cycle.

Describe how the accumulator is used during the Fetch-Decode-Execute cycle.

Describe how the program counter is used during the Fetch-Decode-Execute cycle.

State the name of three other registers that are used during the Fetch-Decode-Execute cycle.

* The charity has several desktop computers in their office that use a CISC processor. They are considering buying mobile devices for their staff to use when they are not in the office.

Discuss whether these mobile devices should use the same CISC processors that are used in their desktop computers or if they should use a RISC processor instead.

You should include the following in your answer:

• the difference between each processor type

• the suitability of each processor type for mobile devices.

OCR Insurance uses a computer system to calculate the price that customers pay for car insurance.

The computer system contains a CPU, GPU, RAM and ROM.

State two factors that affect the performance of a CPU.

Explain the difference between RAM and ROM, including how these are used by the computer system.

Describe one non-graphical use OCR Insurance may have for a GPU.

The CPU uses pipelining to improve efficiency.

Explain what is meant by the term ‘pipelining’.

* OCR Insurance’s computer system uses secondary storage across the company in servers, client machines and for backup purposes.

For each of these, discuss whether magnetic storage or solid state storage would be most suitable, taking into account the advantages and disadvantages of both.

Customers’ details are stored in the flat file database table Customer. An extract of the table is shown below.

State what is meant by the term ‘primary key’, identifying the primary key in the table above.

Write the SQL statement that would show only the CustomerID and Surname fields for customers with the Title “Miss” or “Mrs”.

Describe one problem that would arise with the flat file database structure if a customer wanted to insure more than one car at the same time.

Describe how the flat file database structure could be altered to efficiently allow each customer to insure multiple cars at the same time. (You may assume each car is insured to only one customer.)

A program written in the Little Man Computer instruction set is given below.

State what the program outputs are for the following inputs.

State what the purpose of the program is.

Explain which registers are used and their values when the line STA count is executed and the accumulator is holding the value 9. The label count refers to memory location 16.

Whilst the line STA count is being executed, the CPU receives a signal from another process, requiring its attention.

State the name for the signal received by the CPU.

The code uses direct addressing. Describe one other mode of addressing.

A digital coffee making machine has a CPU that uses the Little Man Computer Instruction Set.

Little Man Computer operates on a computer system based on the Von Neumann Architecture.

State two features of the Von Neumann architecture.

2

Describe one feature, not part of the standard Von Neumann Architecture, which contemporary CPUs may have in order to improve performance.

Part of the coffee making machine’s code asks the user to press a button to select strength. The code outputs 1 which will switch on a green light to indicate a valid selection or outputs 0 to indicate an invalid selection.

The code is shown below:

Tick the appropriate boxes below to indicate which inputs will result in a green light (i.e. code outputs 1) and which with a red light.

Explain which registers and buses are used, and the values they store/carry, when the line LDA redLight is executed (after it has been fetched and decoded). You should assume the address redLight refers to memory location 11.

Write code in a high‑level language or pseudocode that has the same functionality as the code in Fig. 1.

* Discuss the differences between assembly code and high‑level languages. You should refer to:

• the advantages and disadvantages of writing programs in assembly code rather than a high-level language

• when each approach might be used

• why the coffee machine was programmed in assembly code.